Time delay monostable electronic control unit



Feb. 23, 1960 M. D. DE MONG I'IME DELAY MONOSTABLE ELECTRONIC CONTROLUNIT Filed March 22, 1957 mum-annua l INV ENT OR. BY 149. @a

ATI'ORNIW United States Patent Q TIME DELAY MONOSTABLE ELECTRONICCONTROL UNIT Maurice D. De Mong, Torrance, Calif., assignor, by mesneassignments, to the United States of America as represented by theSecretary of the Navy Application March 22, 1957, Serial No. 647,929

1 Claim. (Cl. 25027) This invention relates to a time-delay monostableelectronic control unit and particularly to such a unit responsive to atriggering operation for energizing a relay or other load device and formaintaining such load device actuated for a predetermined time interval.

It is frequently desired to control a relay or other load device inresponse to a series of spaced momentary triggering impulses oroperations and to maintain such relay operative so long as, but only solong as, the spacing between successive triggering impulses does notexceed some predetermined value. 7

It is an object of this invention to provide an electronic control unitcapable of producing this result and which may conveniently becontrolled by momentary triggering operations of a triggering switch.

A further object is to provide such a unit comprising a monostableelectronic fiip-flop unit responsive to operation of a triggering switchto change to its unstable state for a period determined by acapacitor-resistor timing circuit incorporated therein, and effective tomaintain the unit in said unstable state for another such period if thetriggering switch is again actuated before the expiration of the firsttiming period.

Other objects and advantages of my invention will become apparent fromthe following description and claim especially when considered in thelight of the accompanying drawing wherein the single figure is aschematic diagram of an embodiment of the invention.

As shown in the drawing the control unit comprises a first electronictube 1 which controls the operation of a second electronic tube 2 havinga load device such as the coil 3 of a relay 4 in series therewith.Operating voltages for the tubes are obtained from positive terminal 5and negative terminal 6 which are adapted to be connected across asuitable source of DC. potential (not shown).

The cathodes 7 and 8 of tubes 1 and 2 are directly connected togetherand to one end of a common cathode resistor 9 of relatively high value.The anode 10 of tube 1 is connected by resistor 11 to positive terminal5 and by a relatively high value resistor 12 to the grid 13 of tube 2,which grid is in turn connected to negative terminal 6 by resistor 14.

The grid 15 of tube 1 is connected to the positive terminal 5 by a highvalue resistor 16 which constitutes part of the time-controlling portionof the unit. A main timing capacitor 17 has its one side connected tothe negative terminal 6 and its other side to the movable contact 18 ofa single-pole double-throw triggering switch 19, the normally-closedcontact 20 of which is connected to the grid 15 of tube 1. Thenormally-open contact 21 of switch 19 is connected directly to thenegative terminal 6 so that when contact 18 is operated from its normalposition it breaks the circuit from condenser 17 to grid 15 andsimultaneously shunts the capacitor to discharge it.

Switch 19 may be actuated in any way desired, but is shown herein, forpurposes of illustration, as conp 2,926,248 Patented Feb. 23, 1960stituting the switch contacts of a suitable triggering relay applicationof a suitable control pulse thereto will actuate the switch 19 to openthe circuit between movable contact 18 and stationary contact 20 andclose the circuit from contact 18 to contact 21. Deenergization of coil23 will result in return of the switch contact 18 to its normal positionshown in the drawing.

An auxiliary capacitor 24, preferably of considerably lower capacitythan capacitor 17 is connected directly from grid 15 to negativeterminal 6.

With switch 19 in its normal position shown and appropriate voltagesapplied to terminals 5 and 6, the tube 1 will normally be heavilyconducting due to the positive voltage applied to the grid 15 thereof byway of resistor 16. This will cause a relatively large voltage drop toobtain across cathode resistor 9 so that the cathode of tube 2 will beconsiderably positive with respect to its grid 13 and will therefore becompletely cut oil. The grid 15 of tube 1 will be substantially at. thesame potential as its cathode 7 and capacitors 17' and 24 will becharged positively to this same value.. This condition is completelystable and will be main tained until a triggering operation is appliedto switch19..

When, as by application of a short pulse to coil 23,. switch 19 ismomentarily actuated, capacitor 17 will.

be shorted and rapidly discharged to ground potential..

However this will have no ellect upon the unit until.

switch 19 is restored to its normal position upon decay" of thetriggering pulse, whereupon the major portion of. the charge oncapacitor 24 will flow rapidly into capacitor" 17 until the twocapacitors are equalized at a potentiali slightly above ground potentialbut still considerably" below that of cathode 7. This will substantiallyinstantly cut off tube 1, raising the anode potential thereof and%resulting in an increase in potential on the grid 13 off tube 2.Meanwhile the decrease in current through tube: 1 results in a decreasein cathode potential in tube 2.; so that tube 2 will become conductiveto thereby energize-- the relay or load device 4. The cathode potentialofi both tubes will thereupon assume a new value determined?! by thecurrent flow through tube 2. This new value: will however still beappreciably higher than the gridl voltage on tube 1 so that the latterwill remain non-,- conducting.

Meanwhile capacitors 17 and 24 will begin to charge. exponentiallythrough resistor 16, gradually increasing: the grid potential on tube 1until, at a time determined by the circuit constants, the grid 15becomes sufficiently positive to again permit tube 1 to conduct. Theresulting drop in potential on the anode 10 will cause a correspondingdrop in grid potential on tube 2 until a point is reached where tube 2will once again be cut 05, deenergizing load relay 4. The time whichelapses between energization and deenergization of the relay in responseto a triggering impulse may be readily controlled by selection ofappropriate values for resistor 16 and for capacitors 17 and 24.

If, however, a second triggering impulse is applied to switch 19 whilethe unit is still in its unstable state (tube 2 conducting) anothertiming cycle will be initiated and the relay 4 will remain energized.During the momentary actuation of switch 19 to discharge capacitor 17,capacitor 24 will maintain blocking voltage on the grid 15 until switchmember 18 once again returns to its normal position, to initiate a newtiming cycle. Thus tube 1 will remain cut off and tube 2 conducting atleast until the end of the new timing interval.

Thus each actuation of the triggering switch 19 serves to first preparethe unit for a new timing cycle, without affecting the then-existingoperating state of the unit, and then, upon return of the switch to itsnormal position,

actually starts the new timing cycle and, if the load device is notalready energized, energizes the latter, maintaining it energizedfor'the duration of the timing cycle.

While the values of the various components will of I course depend uponthe high voltage available, the tubes gering signals from a sourcethereof, said unit comprising first and second electron discharge tubes,each ha"- ing an anode, a cathode, and a control grid, a first resistordirectly connecting the cathodes of said tubes to the negative side or"said supply, "means for rendering said first tube normally conductiveincluding a second resistor and a third resistor directly connecting theanode and grid respectively of said first tube to the positive side ofsaid supply, a load device connecting the anode of said second tube tothe positive side of said supply, and energized by the output of saidsecond tube, means for rendering said second tube nonconductive Wheneversaid first tube is conductive and conductive whenever said first tube isnonconductive, including a fourth resistor and fifth resistor connectingthe grid of said second tube to the anode of said first tube and to thenegative side of said supply respectively, a first capacitor having oneside thereof connected to the negative side of said supply, asingle-pole double-throw switch having its common terminal connected tothe other side of said first capacitor and movable between a firstposition in which 4 said first capacitor is connected in circuitdirectly between the negative side or" said supply and the grid of saidfirst tube, and a second position in which said circuit is opened andsaid first capacitor is simultaneously shunted directly across thenegative side or" said supply to discharge said first capacitor, meansfor moving said switch to said second position in response to atriggering signal from said source and to said first position in theabsence or a triggering signal from said source, the movement of saidswitch from said second position to said first position biasing the gridof said first tube to render the first tube nonconductive for a periodof time determined by the rate of charge of said first capacitor throughsaid third resistor, and a second capacitor of lower capacity than saidfirst capacitor connected directly between the grid of said first tubeand the negative side of said source to maintain said first tubenonconductive during a subsequent movement of said switch to said secondposition and back to said first position occurring Within said period oftime, whereby said load device is energized in response to eachtriggering signal and remains energized for at least said period of timeafter each triggering signal and for so long as the time intervalbetween successive triggering signals is less than said period of time.

References Cited in the file of this patent UNITED STATES PATENTS FarmerSept. 18, 1951

